Method of grease manufacture



March 22, 1966 G. s. BRIGHT ETAL 3,242,084

I METHOD OF GREASE MANUFACTURE Filed May 22, 1965 Wm w United StatesPatent 3,242,084 METHOD OF GREASE MANUFACTURE Gordon S. Bright, PortArthur, and William R. Green, in, Groves, Tex., assignors to Texacolino, New York, N.Y., a corporation of Delaware Filed May 22, 1963, Ser.No. 282,341 Claims. (Cl. 252-39) This invention relates to an improvedmethod for the manufacture of calcium hydroxy fatty acid soap thickenedgreases of the so-called rheopectic type, which undergo a large amountof hardening upon moderate shearing of the type to which they aresubjected in automotive bearings in service.

In accordance with this invention, low soap content calcium hydroxyfatty acid soap thickened greases of the rheopectic type are prepared bya low temperature method carried out with recirculation of the greasemixture through a recycle line on the grease making zone during theheating up to a maximum temperature below the melting point of the soap,and optionally during the cooling step also. By carrying out the processunder the preferred conditions, which comprise forming a relativelydilute soap slurry and recirculating continuously during at least thatportion of the heating cycle wherein the major amount of fiberdevelopment takes place, with substantially no additional shearing ofthe grease mixture, fluid greases containing as high as about percent,and ordinarily about 2-12 percent by weight of calcium hydroxy fattysoaps are obtained which thicken to N.L.G.I. No. 0-2 grade consistenciesupon moderate shearing.

Calcium hydroxy fatty acid soap thickened greases prepared in theabovemanner contain long well shaped soap fibers in a highly agglomeratedcondition, accounting for the low viscosity of the product. While we ldo not wish to be limited by any theory, it is thought that the effectof the conditions of our process in producing the grease consistencycharacteristics required for a rheopectic grease is due to the increasedtendency of the longer fibers thus produced to form agglomerates,together with the reduced amount of energy input required to redispersethe fibers in these agglomerates due to their smooth fiber form. Theaffect moderate shearing of these greases in producing a large change inconistency is in marked constrast to the effect of such shearing uponcalcium hydroxy fatty acid soap thickened greases obtained by lowtemperature methods of the prior art, whereby little or no change inconsistency is ordinarily obtained by only moderate shearing.

In accordance with the preferred embodiment of our invention, the greasemixture is recirculated continuously during both the heating and coolingcycles and additional oil at a lower temperature is introduced into therecycle stream during the cooling process, as described by L. F.Badgett, W. R. Hencke and F. T. Crookshank in their copendingapplication Serial No. 282,330, filed of even date herewith. The processis also carried out very advantageously by introducing additional oil ata higher temperature than the grease mixture into the recycle streamduring heating to the maximum temperature, as also described in the saidapplication of Badgett et al.

The grease making process of our invention is preferably carried outwith no shearing of the grease mixture obtained by the saponificationstep aside from that necessarily obtained by the recycling operation andthe effect of the stirrer. However, shearing during the saponifioationmay be employed very advantageously in some cases, suitably by means ofa shear valve in the recycle line operated at a pressure drop of about-200 pounds per square inch, preferably at about -125 pounds perPatented Mar. 22, 1966 square inch, where difiiculty is experienced inobtaining a smooth product.

The figure is a diagrammatic illustration of one form of apparatussuitable for making greases in accordance With the preferred embodimentof this invention.

Referring in more detail to the figure, numeral 1 represents a jacketedgrease kettle equipped with stirrer 2 and adapted to be heated toelevated temperatures above about 350 F. In carrying out the greasepreparation, the grease kettle is charged with saponifiable material,lubricating oil, and a calcium metal base, such as calcium oxide,calcium hydroxide or calcium carbonate, in approximately thestoichiometric amount required to react with the saponifiable material.Water may be added to the charge also, suitably in an amount equal tofrom about 0.5 to about five times the weight of the metal base,although the presence of water is not required. The lubricating oil andsaponifiable material are employed in a Weight ratio of at least about2:1, respectively, and preferably at least about 3:1, respectively. Theyare most suitably employed in a weight ratio from about 3:1 to about5:1, respectively.

The kettle contents are heated with stirring up to the maximumtemperature employed, which ordinarily requires about 1-5 hours,including a holding period which is preferably employed in the maxim-umtemperature range for at least about 15 minutes.

Recirculation of the grease mixture through the recycle line is carriedout during the heating at least up to about 240 F. and is begun at leastas soon as dehydration is substantially complete. It is preferably begunat least as soon as the saponification is substantially complete.Recirculation of the grease mixture is begun by turning valves 6 and 8to the open position and starting pump 12. The grease mixture passesthrough line 5 containing valve 6 line 10 containing valve 8, pump 12,and line 14 containing pressure gauge 15 and shear valve 19, which issuitably a gate valve. Valve 19 is located a suffioient distance fromkettle 1 to avoid spraying of the grease mixture into the kettle whenthe valve is operated under a back pressure, suitably a distance equalto at least about 12 times the diameter of pipe 14. Lines 5, 10 and 14may be jacketed or otherwise provided with means for applying additionalheating and cooling to the recirculating stream of grease mixture. Pump12 is preferably of a type wherein the fluid being pumped is subjectedto only a relatively small amount of sheaning. It is suitably a positivedisplacement rotary type pump wherein the grease mixture is sheared at arate below about 10,000 reciprocal seconds and preferably at a ratebelow about 5,000 reciprocal seconds.

In carrying out the process by the preferred embodiment of thisinvention, the grease mixture: is circulated continuously during thesaponification and during the remainder of the heating cycle and thecooling cycle also, with valve 19 in the wide open position followingthe saponification step. During the saponification step, valve 19 may bein a partly closed position so as to give a pressure drop of about20-200 pounds per square inch, and very suitably in about the range25-125 pounds per square inch across the valve. Shearing of the recycledstream may be continued in this manner for a short period following thesaponification step, preferably for a period not in excess of about 15minutes and before the grease mixture has been heated above about 240 F.Such a procedure is useful in some cases in. the preparation of greaseswhich are particularly difficult to prepare in satisfactorily smoothform. However, it is not ordinarily necessary or desirable, and ourpreferred procedure involves no substantial shearing of the greasemixture following the saponification step.

Circulation of the grease mixture through the recycle system during theheating cycle following the saponification step is carried out at a ratesufiicient to give one batch turnover within about 22 minutes, such asin about 03-22 minutes, and preferably in about 04-15 minutes, based onthe weight of the grease mixture during the heating cycle, or in about0.25-10 minutes, and preferably 0.3-12 minutes, based upon the averageweight of grease mixture during the heating cycle when the process iscarried out with additional oil added during the heating step asdescribed hereinbelow. Recycling during the cooling cycle is suitablycarried out at a rate sufficient to provide a batch turnover in about0.535 minutes, and preferably in about l20 minutes, base on the weightof the finished grease, or in about 0.427 minutes, and preferably about05-17 minutes, based on the average weight of grease mixture during thecooling cycle.

Very advantageously, the recycling is carried out for a minimum periodof about 15 minutes, and preferably for at least about 30 minutes duringthe heating cycle following the saponification, until at least 5 batchturnovers and preferably at least batch turnovers, based on the averageweight of the grease mixture during this period, are obtained.

The maximum temperature to which the grease mixture is heated isordinarily in the range from about 250 F. to just below the meltingpoint of the soap. In the preparation of calcium 12-hydroxystearatethickened greases employing paratfinic lubricating oils, the greasemixture is preferably heated to a top temperature in the range fromabout 260 F. to about 275 F. The grease mixture is usually heated withinthis temperature range for a time from about 15 minutes to about 2hours. However, in some cases the process may be carried out with noholding period in the high temperature range.

Cooling of the grease mixture is carried out by cutting off the heat tothe kettle, and to the recycle line if such additional heating isemployed, and introducing lubricating oil from tank into therecirculating stream of grease mixture. The added oil is at atemperature substantially below that of the grease mixture, such as atleast about 100 F., and preferably at least about 150 F. below thetemperature of the grease mixture at the beginning of the cooling step.The lubricating oil passes from tank 20 into line 36 by way of line 22containing valve 23, pump 24, line 25 and line 26 containing valve 27,dial thermometer 33, pressure gauge 34 and valve 35. Valve 35 ispreferably a one way valve, most suitably of a type designed to preventgravity flow of oil through pump 24 when the pump is not operating, suchas a diaphragm controlled reducing valve or a spring loaded check valve.In line 36, the oil may pass into the recirculating stream of greasemixture at the intake of pump 12 by passing through valve 37 into line10, or into the grease mixture at the discharge side of pump 12 bypassing through valve 38 into line 14. It is preferably passed into thegrease mixture at the intake side of pump 12 in order to obtainincreased mixing by the action of the pump. The oil may be introducedinto the recirculating stream of grease mixture at a rate such that theratio of the rate of flow of the grease mixture before the point ofconfluence to the rate of oil addition is from about 1:1 to about 400:1, preferably in a ratio from about 2:1 to about 150:1, and mostadvantageously in a ratio from about 3:1 to about 1, by weight,respectively.

The oil addition is preferably commenced at the beginning of the coolingstep and may be carried out over the entire cooling period or duringonly a portion thereof. Additional cooling may be applied to the kettle,and also to the recirculating stream of grease mixture. The amount oflubricating oil added during the cooling may amount to from about 10 toas high as about 90 percent of the total oil contained in the grease. Itwill usually be from about 25 to about 75 percent of the total oilcontained in the grease. Any additives employed in the 4. grease may beadded during the cooling step, preferably when the grease mixture hasbeen cooled to about 250 F. or lower. The cooled grease mixture isfinally drawn through line 40 containing valve 41.

In the grease preparation carried out by the method comprising aparticularly preferred embodiment of this invention, the saponificationis carried out in the presence of lubricating oil in a ratio from about2:1 to about 4:1, respectively, with the saponifiable material, andpreheated oil is introduced into the recirculating stream of greasemixture during the heating step, preferably beginning when the greasemixture is at a temperature in about the range 220-250 F. in .an amountsuflicient to give an oil-soap ratio of at least about 5:1 andpreferably from about 7:1 to about 12:1, respectively. The added oil ispreferably preheated to a temperature substantially above thetemperature of the grease mixture as a means of rapidly bringing thegrease mixture up to the top temperature. The preheated oil isintroduced into the recycle line by passing from tank 20 to heater 30 byway of line 22, pump 24, line 25 and line 28 containing valve 29. Heater30 may be any suitable type of heater, such as a coil heater asindicated in the diagram. From heater 30 the oil passes into line 26 andis introduced into the circulating stream of grease mixture at eitherthe intake or the discharge side of pump 12 as described hereinabove inconnection with the introduction of the oil during cooling. Thetemperature of the oil added in this manner is preferably substantiallyhigher than that of the grease mixture, and may be up to or evenslightly higher than the melting point of the soap in some cases. Therate at which this oil is introduced may suitably be such that the ratioof the rate of recirculation of the grease mixture to the rate of oilinjection is within the ranges disclosed hereinabove in connection withthe introduction of cold oil during the cooling cycle. The amount of oiladded in this manner may be up to about 70 percent of the total oilemployed in the grease. It is ordinarily from about 20 to about percentof the total oil contained in the finished grease.

Suitable soap forming hydroxy fatty acid materials which may be employedin the production of these greases are essentially saturated hydroxyfatty acids containing 12 or more carbon atoms and one or more hydroxylgroups separated from the carboxyl group by at least one carbon atom,the glycerides and lower alkyl esters of such acids. Preferably, theacid contains about 16 to about 22 carbon atoms per molecule. Suchmaterials may be obtained from naturally occurring glycerides orproduced synthetically by methods such as the 'hydroxylation of fattyacids or the hydrogenation of ricinoleic acid or castor oil.Particularly suitable materials of this character are l2-hydroxystearicacid, the methyl ester thereof, and hydrogenated castor oil.

The lubricating oils employed in these greases include particularly theconventional mineral lubricating oils, having Saybolt Universalviscosities in the range from about seconds at 100 F. to about 225seconds at 210 F., and synthetic hydrocarbon oils having viscosities inthis range, such as those obtained by cracking and po lymerizingproducts of the Fiseher-Tropsch process and the like. The minerallubricating oils may be either naphthcnic or paraffinic oils, or blendsof different oils of these types. Other synthetic oleaginous compoundssuch as polyesters, polyethers, etc. having viscosities within thelubricating oil viscosity range may also be employed in these greases asat least part of the lubricating oil component. Suitable compounds ofthis type include particularly the aliphatic dicarboxylic acid diesters,such as, for example, di-Z-ethylhexyl sebacate, di(secondary amyl)sebacate, di-2-ethylhexyl azelate, di-iso-octyl adipate, etc. However, alubricating oil which is substantially unreactive under thesaponification conditions is preferably employed in the saponificationmixture, mineral lubricating oils being particularly suitable for thispurpose,

Various additives of the usual types, such as corrosion inhibitor-s,oxidation inhibitors, extreme pressure agents, antiwear agents, etc.,may be employed in these greases. Suitable oxidation inhibitors includeparticularly those of the amine type, such as diphenylamine,phen'ylalpht'u napthylamine, tetramethyl diaminodiphenyl methane, etc.Very advantageously, the greases may contain from about 3 to 12 percentby weight of a sulfurized fatty oil, such as sulfurized sperm oil,containing about 5-15 percent by weight of sulfur, and about 1 to 3percent by weight of a lead soap, such as lead naphthenate. Leadnaphthenates obtained from relatively low molecular weight naphthenicacids, such as those having molecular weights in about the range fromabout 120 to 235, and preferably in the range from about 200 to about230, are particularly suitable for this purpose. By means of thisadditive combination, good extreme pressure properties are imparted tothese calcium hydroxy fatty acid soap greases without any substantialimpairment of their rheopectic properties.

The following example is illustrative of grease preparations carried outin accordance with the preferred embodiment of this invention.

Example I A calcium 12-hydroxystearate grease was prepared in the mannerdescribed below.

The equipment employed in the preparation of this grease was a 150 poundcapacity steam-heated laboratory kettle with auxiliary equipment forgrease circulation with oil injection into the recycle stream as shownin FIG. 1. The circulation equipment consisted of a 1% inch pipeconnecting the kettle drawoff with .a No. 2 Globe Rota Piston pumphaving a capacity of 1 gallon per 100 revolutions, or 18 gallons perminute, and a inch pipe extending from the pump to the top of thekettle.

In carrying out the grease preparation, the grease kettle was chargedwith 7 pounds of 12-hydroxystearic acid having a neutralization numberof 179, a saponification number of 187 and an iodine number of 5, and 28pounds of a refined paraflinic distillate oil having a Saybolt Universalviscosity at 100 F. of 342 seconds and a viscosity index of 93.5.Stirring of the mixture was begun, and one pound of lime with an equalweight of water were added to the mixture. Heating of the kettle wasthen begun and circulation of the grease mixture through the recycleline also was begun at a rate of 120 pounds per minute. The mixture washeated up to about 220 F. in about 35 minutes, at which time foaming hadstopped. Injection of 28 pounds of the paraflinic oil into the recyclestream at the intake side of the pump was then begun at a rate of 50pounds per hour while the temperature was maintained at about 220 F. bykettle heating. The mixture was then heated up to 250 F. in about 1 hourand maintained at 250 to 273 F. for about 72 minutes with continuedrecirculation and stirring. The heat was then cut off and 62.75 poundsof the lubricating oil were added in the same manner at a rate of 50pounds per hour while the temperature dropped from 273 to 195 F. inabout 79 minutes. A fluid product was obtained which was too soft forpenetration tests.

The above product was changed into a smooth buttery N.L.G.I. No. 1 gradegrease by moderate shearing as shown by the following tabulation:

tration (about 448) 6 Milled, 1 pass through Premier Colloid Mill at0.003 in. clearance Unworked 303. Worked, 60 strokes 338.

circulated through shear valve at 60 p.s.i.-g. pressure drop for 1 /2hrs.-

Unworked 306. Worked 33.9. After /2 hr. in Marlin Rockwell Bearing Test,1750 rpm. 32.2.

Obviously, many modifications and variations of the invention, asherein-before set forth, may be made without departing from the spiritand scope thereof, and, therefore, only such limitations should beimposed as are indicated in the appended claims.

We claim:

1. The process of preparing a rheopectic lubricating grease comprisingessentially a lubricating oil as the chief component and a greaseforming amount of calcium 12- hydroxy stearate, which comprisesessentially saponifying a 12-hydroxy stearic acid material with a basiccalcium compound at a mildly elevated temperature in the presence of aparaffinic lubricating oil which is substantially non-reactive under thesaponification cdnditions in an amount equal to at least about 2 timesthe weight of the said saponifiable material, heating the grease mixturethus obtained up to a maximum temperature in the range from about 260 F.to 275 F. and below the melting point of the soap in from about 1 toabout 5 hours with the addition of any additional amount of lubricatingoil required to give an oil-soap ratio of at least about 5:1,respectively, and thereafter cooling the said grease mixture with theaddition of additional lubricating oil at a substantially lowertemperature than the grease mixture, said heating following thesaponification and substantial dehydration in the temperature range upto at least about 240 F. being carried out upon a maintained body of thesaid grease mixture in a grease making zone with continuousrecirculation of the grease mixture through an external recycle line ata rate such that the weight of grease mixture recirculated is at leastequal to the total weight of grease mixture within about 22 minutes,said process being carried out without any substantial shearing of thegrease mixture during the said heating at above about 240 F. and duringthe said cooling other than that resultingfrom stirring andrecirculating the grease mixture through the said recycle .line.

2. The process of claim 1 wherein the said heating step is carried outwith continuous recirculation of the said grease mixture at a rate suchthat the weight of recirculated grease mixture equals the total Weightof grease mixture in about 04-15 minutes.

3. The process of claim 1 wherein the saponification step is carried outwith continuous shearing of the saponification mixture.

4. The process of claim 1 wherein the saponification is carried out inthe presence of lubricating oil in an amount from 2 to about 4 times theweight of the saponifiable material and additional lubricating oil isadded after the dehydration is substantially complete in an amountsufiicient to provide an oil-soap mixture comprising lubricating oil inan amount from about 7 to 12 times the weight of the said soap.

5. The process of claim 3 wherein the said additional lubricating oil ispreheated to a temperature above the temperature of the grease mixture.

6. The process of claim 1 wherein the said saponifiable material is12-hydroxystearic acid.

7. The process of preparing a fluid lubricating grease comprisingessentially a mineral lubricating oil as the 7 chief componentcontaining about 2-12 percent by weight of calcium 12-hydroxystearateand having the property of thickening to a grease consistency uponshearing, which comprises essentially saponifying a 12-hydroxy'stearicacid material with a basic calcium compound at a mildly elevatedtemperature in the presence of mineral lubricating oil in an amountgiving a weight ratio with the said 1- hydroxystearic acid material from2:1 to 4: 1, respectively, heating the grease mixture thus obtained upto a maximum temperature in the range from about 260 F. to about 275 F.in about 15 hours While adding additional mineral lubricating oil in anamount sufficient to give an oil-soap ratio from about 7:1 to about12:1, respectively, and thereafter cooling the grease mixture with theaddition of additional mineral lubricating oil at a lower temperaturethan the grease mixture, said heating and cooling being carried out upona maintained body of the said grease mixture in a grease making zonewith continuous recirculation of the grease mixture through an externalrecycle line at a rate such that the weight of grease mixturerecirculated during the heating cycle is equal to the total averageweight of grease mixture in the heating cycle in about 0.2515 minutes,said process being carried out with no substantial shearing of thegrease mixture during the said heating and cooling other than thatresulting from stirring and recirculating the grease mixture through thesaid recycle line.

. 8. The process of claim 7 wherein the oil-added during the heating andcooling steps is introduced into the said recycle line.

9. The process of claim 7 wherein the oil added during the heating is ata temperature above the temperature of the grease mixture but below themelting point of the soap.

10. The process of claim 7 wherein the saponification is carried outwith continuous circulation of the saponification mixture through ashear valve with a pressure drop of about 25-125 pounds per square inch.

References Cited by the Examiner UNITED STATES PATENTS 2,332,202 10/1943Calkins 25242.1 2,450,220 9/1948 Ashburn et al 252-41 2,830,022 4/1958Nelson et al. 252-41 2,870,090 1/1959 Pitman et al. 25239- 2,886,5255/1959 Dilworth et al. 25239 3,015,624 1/1962 Hencke et al. 252413,068,174 12/1962 Pelton et al 25239 3,068,175 12/1962 Roach et a].25239 3,079,341 2/1963 Coons et al. 25241 3,117,087 1/1964 McCormick eta1 25241 DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner.

1. THE PROCESS OF PREPARING A RHEOPECTIC LUBRICATING GREASE COMPRISINGESSENTIALLY A LUBRICATING OIL AS THE CHIEF COMPONENT AND A GREASEFORMING AMOUNT OF CALCIUM 12HYDROXY STEARATE, WHICH COMPRISESESSENTIALLY SAPONIFYING A 12-HYDROXY STEARIC ACID MATEIAL WITH A BASICCALCIUM COMPOUND AT A MILDLY ELEVATED TEMPERATURE IN THE PRESENCE OF APARAFFINIC LUBRICATING OIL WHICH IS SUBSTANTIALLY NON-REACTIVE UNDER THESAPONIFICATION CONDITIONS IN AN AMOUNT EQUAL TO AT LEAST ABOUT 2 TIMESTHE WEIGHT OF THE SAID SAPONIFIABLE MATERIAL, HEATING THE GREASE MIXTURETHUS OBTAINED UP TO A MAXIMUM TEMPERTURE IN THE RANGE FROM ABOUT 260*F.TO 275*F. AND BELOW THE MELTING POINT OF THE SOAP IN FROM ABOUT U TOABOUT 5 HOURS WITH THE ADDITION OF ANY ADDITIONAL AMOUNT OF LUBRICATINGOIL REQUIRED TO GIVE AN OIL-SOAP RATIO OF AT LEAST ABOUT 5:1,RESPECTIVELY, AND THEREAFTER COOLING THE SAID GREASE MIXTURE WITH THEADDITION OF ADDITIONAL LUBRICATING OIL AT A SUBSTANTIALLY LOWERTEMPERATURE THAN THE GREASE MIXTURE, SAID HEATING FOLLOWING THESAPONIFICATION AND SUBSTANTIAL DEHYDRATION IN THE TEMPERATURE RANGE UPTO AT LEAST ABOUT 240*F. BEING CARRIED OUT UPON A MAINTAINED BODY OF THESAID GREASE MIXTURE IN A GREASE MAKING ZONE WITH CONTINUOUSRECIRVULATION OF THE GREASE MIXTURE THROUGH AN EXTERNAL RECYCLE LINE ATA RATE SUCH THAT THE WEIGHT OF GREASE MIXTURE RECIRCULATED IS AT LEASTEQUAL TO THE TOTAL WEIGHT OF GREASE MIXTURE WITHIN ABOUT 22 MINUTES,SAID PROCESS BEING CARRIED OUT WITHOUT ANY SUBSTANTIAL SHEARING OF THEGREASE MIXTURE DURING THE SAID HEATING AT ABOVE ABOUT 240*F. AND DURINGTHE SAID COOLING OTHER THAN THAT RESULTING FROM STIRRING ANDRECIRCULATING THE GREASE MIXTURE THROUGH THE SAID RECYCLE LINE.